Chocolate chip cookies, red velvet cake, raisin bread and our favourite baked goods all have one thing in common: flour. According to Wheat World, flour has been used in some form since the beginning of civilisation. The most common type of flour in the grocery store is all-purpose flour, which comes in bleached and unbleached varieties. Each has its own benefits, depending upon what you're trying to make.
Unbleached flour has a yellowish tone, the natural colour of the wheat used to make it. Bleached flour is pure white because of the bleaching agent used on it. White flour is sometimes more desirable in certain recipes such as white cake and white breads.
Bleached flour is typically bleached with a chlorine oxide that is safe to consume. Aside from whitening the flour, bleaching speeds up the ageing process of flour, making it ready to use faster. Freshly milled flour is not yet ready to be used and needs to age to improve the texture. Bleaching shortens the ageing time of flour from 12 weeks to 48 hours, according to The Foodie File, which is why it is used so often in commercial cooking.
Unbleached flour actually also goes through a bleaching process as well, just naturally. Unbleached flour bleaches itself by natural oxidation over a 12-week ageing process, in which it turns progressively whiter. It still has an off-white appearance. Over time, however, unbleached flour will naturally dull, while bleached flour will remain pure white.
Volume and Texture
Bleached flour creates breads and baked goods with more volume than unbleached flour, so the two are not quite interchangeable in recipes. Bleached flour also has a finer texture that makes it more appealing to cook with than unbleached flour, which can have a clumpier feel.
According to a taste test done by Cooks Illustrated, some people found that bleached flour has a slightly "off" taste, or a slightly metallic flavour, because of the chemicals used to bleach it.
Gluten is formed from the protein in flour and is needed to give baked goods the proper structure. Unbleached flour is higher in protein, which creates a chewy texture in baked goods and makes it ideal for yeast-raising foods such as breads as well as in delicate pastries like danishes, eclairs and cream puffs. Bleached flour has far less protein, which is ideal in baked goods for which a chewy texture is not desirable, such as cake, pancakes, waffles, pie crust and cookies.